The combination of microwave cooking and preprocessed food products would appear to promise the enticing advantages of convenience and quick results which could be heightened if such food products were shipped, displayed, cooked, and served in the same package. Unfortunately, these enticing advantages are illusory because certain types of food products, when heated by microwaves, lack many of the characteristics which consumers have come to associate with such products when heated in conventional ovens. The configuration and materials of the package can have a substantial effect upon the results of microwave cooking, but no package has been found which produces entirely satisfactory results when used during microwave cooking of particular foods, such as flour-based food products. Particularly unsatisfactory results occur when such food products are somewhat oval, round, or otherwise irregular in shape, such as rolls, buns, or waffles. To be acceptable, such cooked products must be internally heated without overcooking and must be browned on top, and, if a crust is present, they must be both crisp and brown while avoiding both an overcooked, dried, scorched, burned, or charred effect and an undercooked, cold, doughy effect.
One attempt to solve some of the problems discussed above is disclosed in the patent to Brastad (U.S. Pat. No. 4,267,420). This patent teaches a method for achieving microwave browning of a food item to be heated in a microwave oven by using a packaging material made of a plastic film or other dielectric substrate of sufficient flexibility to allow conformance to the shape of the food item, wherein the conversion of microwave energy to thermal energy occurs in a proximal relationship with the surface portion of the food item. The material, which is flexible, can be supported exteriorly by more rigid dielectric material, such as paperboard. As can be seen in FIG. 3, the overlapping surfaces of the packaging material provide a double heater area on the bottom side of the package. However, Brastad fails to recognize the desirability of providing a container which is shaped and arranged to cause a double heater area to be located in a position beneath the surface area of a food item which affords sufficient shielding to the double heater area by the food item, when the food item and the container are placed in a microwave oven.
Although a number of patents, such as those to Brown, et al. (U.S. Pat. No. 4,590,349) and Maroszek (U.S. Pat. 4,594,492), disclose microwave paperboard packages for use in cooking food products having nonuniform dimensions, including microwave interactive layers for converting microwave energy to heat so as to achieve browning of the food contained therein, none of these packages is suitable both for surface heating contents having an oval, round, or otherwise irregular shape and for browning and crisping food products without the risk of scorching of the package and subsequent scorching of the food due to overlapping microwave interactive layers which generate excess heat when exposed to microwave energy and the risk of excessive shielding due to overlapping which causes generally unpredictable microwave interactivity.
Thus, it has remained an elusive goal in the microwave container art to produce a "cook-in" package for food products having oval, round, or otherwise irregular shape wherein the package is inexpensive, simple to manufacture, disposable and capable of surface heating the food while simultaneously satisfactorily browning and/or crisping the food, and preventing the scorching of the package and subsequent scorching and/or undesirable heating of the food due to overheating of the package's overlapping interactive layers which generate excess heat when exposed to microwave energy.